Cook the pasta according to package directions until al dente. Reserve a cup of pasta water before draining, then drain and set aside.

Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook, stirring frequently, until softened and translucent, about 4–5 minutes.

Add the sliced mushrooms and spread them into a single layer. Cook without stirring for 2 minutes, then stir and continue cooking until the mushrooms have released their liquid and it has fully evaporated, about 8–10 minutes total. Add the minced garlic and red pepper flakes and cook for 1 more minute.

Pour in the white wine and scrape up any browned bits from the bottom of the pan. Let the liquid reduce by half, about 1 minute. Add the vegan butter and let it melt completely, then sprinkle the flour over the vegetables and stir to coat. Cook for 1 minute to eliminate the raw flour taste.

Slowly pour in the vegetable broth a little at a time, stirring continuously after each addition to prevent lumps. Once all the broth is incorporated, stir in the coconut milk, soy sauce, and thyme.

Bring the sauce to a gentle simmer and cook, stirring occasionally, until thickened to a creamy consistency, about 3–4 minutes. If the sauce becomes too thick, loosen it with a splash of reserved pasta water.

Add the cooked pasta to the skillet and toss well to coat every piece in the sauce. Taste and adjust salt and pepper as needed.

Serve immediately, garnished with fresh thyme leaves.